RNA physiology in the eukaryotes is an intriguing and complex problem. We are studying gene products that are thought to mediate aspects of gene expression and RNA biogenesis. These are members of two families, one comprised of the proteins of the HnRNP complex and the other consisting of cMyc and its relatives. Myc gene products are also implicated in the regulation of cellular growth control, but the connection between this property and its capacity to influence gene expression is not yet understood. The experimental system of choice for this work is Xenopus because it provides the opportunity to study these molecules in the context of oogenesis and embryogenesis, and also because it affords some important technical advantages. Initial experiments proposed here will provide molecular level descriptions of gene and protein structure and the patterns of expression during development and differentiation. These studies set the stage for subsequent experiments which focus increasingly on the function and regulation of RNP and myc genes and proteins. Another major goal is to continue development of antisense nucleic acid analysis. This is a potentially general technique for establishing and studying cells or individual organisms that are depleted in a specific gene product. The goal is to bridge the gap between knowledge of gene structure and expression on the one hand, and an understanding of the function of the gene product on the other hand. In some cases antisense analysis may also reveal regulatory circuits governing a particular gene or protein. This aspect of antisense nucleic acid studies is considered further in one st of experiments. A final aim is to apply antisense analysis to the RNP and Myc gene products that are already being studied by more conventional means. Several different parameters can be quantiated to describe phenotypic changes caused by altered expresion of these gene products. This is an important feature that makes them better targets than are genes whose function can only be evaluated by gross phenotypic changes.